checking if Promise is defined before trying to use it

lib/stores/memory.js

@@ -4,7 +4,7 @@ var memoryStore = function(args) {
     args = args || {};
     var self = {};
     self.name = 'memory';
-    self.usePromises = !args.noPromises;
+    self.usePromises = (typeof Promise === 'undefined' || args.noPromises) ? false : true;
 
     var ttl = args.ttl;
     var lruOpts = {